I'm currently in first in a 10 team 5x5 roto mid-season league. I'm pretty satisfied with my team. I'm not necessarily looking to make any trades, but wanted some input on any areas of upgrade that anyone can see to secure my position in the league standings. My roster is as follows:

I've tried to pick up another closer, but other teams either will not trade or are asking ridiculously high returns. I'm currently 5th in saves, with a 3 save lead over sixth. Any help will be appreciated. Specific suggestions of players to use in upgrades are encouraged.
Thanks.